Co-simulation between ESP-r and TRNSYS

The quest for innovative architectural designs and the development of novel and integrated energy conversion, storage, and distribution technologies presents a challenge for existing building performance simulation (BPS) tools. No single BPS tool offers sufficient capabilities and the flexibility to resolve all the possible design variants of interest. The development of a co-simulation between the ESP-r and TRNSYS simulation tools has been accomplished to address this need by enabling an integrated simulation approach that rigorously treats both building physics and energy systems. The design, verification, and demonstration of this new co-simulation environment are demonstrated in this paper.     

Development and application of an updated whole-building coupled thermal,airflow and contaminant transport simulation program (TRNSYS/CONTAM)

The TRNSYS energy analysis tool has been capable of simulating whole-building coupled heat transfer and building airflow for about 10 years. The most recent implementation was based on two TRNSYS modules, Type 56 and Type 97. Type 97 is based on a subset of the airflow calculation capabilities of the CONTAM multizone airflow and contaminant transport program developed by the National Institute of Standards and Technology. This paper describes the development of new CONTAM capabilities in support of an updated combined, multizone building heat transfer, airflow and contaminant transport simulation approach using TRNSYS. It presents an illustrative case that highlights the new coupling capability and also presents the application of this coupled simulation approach to a practical design problem of the energy use related to airflow through entry doors in non-residential buildings.     

Inter-model comparison of embedded-tube radiant floor models in BPS tools

Hydronic radiant floor heating and cooling can potentially reduce energy consumption in buildings. Numerous building performance simulation (BPS) tools contain models for predicting the heat transfer between embedded-tube radiant floor systems and building thermal zones. However, the accuracy, limitations, and methodologies of these models, and their implementations into BPS tools, have never been contrasted in the literature. This paper describes the approaches employed by TRNSYS, ESP-r, and EnergyPlus for modelling embedded-tube radiant floors. An inter-model comparison is then presented for test cases designed to explore model performance. The predictions from the three BPS tools are compared to each other as well as to predictions made with a transient stand-alone finite element analysis tool. Significant issues are identified with the embedded-tube radiant floor models in all three BPS tools.     

Decision-making through performance simulation and code compliance from the early schematic phases of building design

This paper is about the merging of two software applications that allows building decision makers to consider code compliance and to use performance simulation tools from the early schematic phases of building design. By making the capabilities of a code compliance tool available at the early schematic phases of building design, the hope and expectation is that users will use this software to address the mandatory code compliance issues and thus have an opportunity to address other performance issues as well.     

EnergyPlus: creating a new-generation building energy simulation program

Many of the popular building energy simulation programs around the world are reaching maturity — some use simulation methods (and even code) that originated in the 1960s. For more than two decades, the US government supported development of two hourly building energy simulation programs, BLAST and DOE-2. Designed in the days of mainframe computers, expanding their capabilities further has become difficult, time-consuming, and expensive. At the same time, the 30 years have seen significant advances in analysis and computational methods and power — providing an opportunity for significant improvement in these tools.In 1996, a US federal agency began developing a new building energy simulation tool, EnergyPlus, building on development experience with two existing programs: DOE-2 and BLAST. EnergyPlus includes a number of innovative simulation features — such as variable time steps, user-configurable modular systems that are integrated with a heat and mass balance-based zone simulation — and input and output data structures tailored to facilitate third party module and interface development. Other planned simulation capabilities include multizone airflow, and electric power and solar thermal and photovoltaic simulation. Beta testing of EnergyPlus began in late 1999 and the first release is scheduled for early 2001.     

Analysis of energy demand in residential buildings for different climates by means of dynamic simulation

The aim of the present paper is to propose an analysis of energy consumption of a standard building in different climates. The analysis is developed by simulating the dynamic behaviour of the building subjected to different climatic conditions according to the considered location. Simulations are performed by means of an in-house developed code, validated by comparison with the outcomes from leading software, particularly TRNSYS and EnergyPlus. The use of a self-developed code guarantees a high flexibility and allows the implementation of new capabilities if necessary. The impact on the energy consumption of various parameters, namely internal and external wall insulation, window surface areas, thermal capacity and orientation, is investigated. Results show that the insulation of external walls has a fundamental role in reducing energy consumption, because it allows to exploit the thermal capacity of the walls. This is particularly useful for buildings which necessitate to keep the internal temperature constant.     

Co-simulation of innovative integrated HVAC systems in buildings

Integrated performance simulation of buildings' heating, ventilation and air-conditioning (HVAC) systems can help in reducing energy consumption and increasing occupant comfort. However, no single building performance simulation (BPS) tool offers sufficient capabilities and flexibilities to analyse integrated building systems and to enable rapid prototyping of innovative building and system technologies. One way to alleviate this problem is to use co-simulation, as an integrated approach to simulation.

This article elaborates on issues important for co-simulation realization and discusses multiple possibilities to justify the particular approach implemented in the here described co-simulation prototype. The prototype is validated with the results obtained from the traditional simulation approach. It is further used in a proof-of-concept case study to demonstrate the applicability of the method and to highlight its benefits. Stability and accuracy of different coupling strategies are analysed to give a guideline for the required coupling time step.     

Empirical validation and modelling of a naturally ventilated rainscreen façade building

In this paper the thermal behaviour of a rainscreen ventilated façade has been investigated both experimentally and numerically. Field measurements were performed during the 2009/10 winter season in a test building located in San Mauro Pascoli (Italy) having a squared base of internal dimension of 2.89 m and a total internal height of 7.75 m. The external walls of this tower are rainscreen ventilated façades with a 24 cm air cavity and an external side composed of stoneware with open joints. Ventilation grills are located at the top and at the bottom of the tower. In this work the modelling of the test building using a dynamic thermal simulation program (ESP-r) is presented and the main results discussed. In order to study the rainscreen ventilated façade three different multi-zone models were defined and the comparison with the experimental results has been used in order to select the best ESP-r air flow network for the modelling of this kind of envelope component. The thermal analysis of this envelope component evidenced that the ventilated façade is able to reverse the direction of the heat flux through the envelope in regions characterized by large solar irradiation during the winter and moderate wind velocity, when the indoor-outdoor air temperature difference is small, thereby reducing the energy consumption required for indoor heating.     

Investigation of the performance of a ventilated wall

The need for environmental friendly and energy efficient building design has stimulated the design of new facade technologies, including various configurations of double skin facades. This paper investigates the thermal performance of a ventilated wall, both for heating and cooling. A thermal analysis was carried out, paying special attention to the characterization of the heat convection resulting from the buoyancy-induced flow in the open air channel which proved to be a critical aspect of the ventilated wall's behaviour. An integrated thermal and air flow model for the entire system was developed. A model of the ventilated wall construction was developed with the ESP-r simulation program and checked against experimental data from a real-scale test cell facility.The thermal benefits of adding a radiant barrier layer were also investigated. The results showed that this layer was beneficial in terms of the energy performance of the construction. Also, the comparison between the experimental and simulation model results showed satisfactory levels of convergence with the exception of the night hours during the summer period. A sensitivity analysis was also undertaken in order to investigate the main factors and the extent of their effect on the temperature variation inside the ventilated facades.     

History and development of validation with the ESP-r simulation program

It is well recognised that validation of dynamic building simulation programs is a long-term complex task. There have been many large national and international efforts that have led to a well-established validation methodology comprising analytical, inter-program comparison and empirical validation elements, and a significant number of tests have been developed. As simulation usage increases, driven by such initiatives as the European Energy Performance of Buildings Directive, such tests are starting to be incorporated into national and international standards. Although many program developers have run many of the developed tests, there does not appear to have been a systematic attempt to incorporate such tests into routine operation of the simulation programs. This paper reports work undertaken to address this deficiency. The paper summarizes the tests that have been applied to the simulation program ESP-r. These tests have been developed within International Energy Agency Annexes, within CEN standards, within various large-scale national projects, and by the UK's Chartered Institution of Building Services Engineers. The structure used to encapsulate the tests allows developers to ensure that recent code modifications have not resulted in unforeseen impacts on program predictions, and allows users to check for themselves against benchmarks.     

Integrating power flow modelling with building simulation

The inclusion of photovoltaic facades and other local sources of both heat and power within building designs has given rise to the concept of embedded generation: where some or all of the heat and power demands are produced close to the point of use. This paper describes recent work to simulate the heat and power flows associated with both an embedded generation system and the building it serves. This is achieved through the development of an electrical power flow model and its integration within the ESP-r simulation program.     

Computational intelligence techniques for HVAC systems: A review

Buildings are responsible for 40% of global energy use and contribute towards 30% of the total CO2 emissions. The drive to reduce energy use and associated greenhouse gas emissions from buildings has acted as a catalyst in the development of advanced computational methods for energy efficient design, management and control of buildings and systems. Heating, ventilation and air-conditioning (HVAC) systems are the major source of energy consumption in buildings and ideal candidates for substantial reductions in energy demand. Significant advances have been made in the past decades on the application of computational intelligence (CI) techniques for HVAC design, control, management, optimization, and fault detection and diagnosis. This article presents a comprehensive and critical review on the theory and applications of CI techniques for prediction, optimization, control and diagnosis of HVAC systems. The analysis of trends reveals that the minimisation of energy consumption was the key optimization objective in the reviewed research, closely followed by the optimization of thermal comfort, indoor air quality and occupant preferences. Hardcoded Matlab program was the most widely used simulation tool, followed by TRNSYS, EnergyPlus, DOE-2, HVACSim+ and ESP-r. Metaheuristic algorithms were the preferred CI method for solving HVAC related problems and in particular genetic algorithms were applied in most of the studies. Despite the low number of studies focussing on multi-agent systems (MAS), as compared to the other CI techniques, interest in the technique is increasing due to their ability of dividing and conquering an HVAC optimization problem with enhanced overall performance. The paper also identifies prospective future advancements and research directions.     

Domain integration in building simulation

To facilitate multi-variate performance appraisal all aspects of a building must be treated simultaneously. This paper gives examples of how the principal technical domains relating to a building’s environmental performance are coupled within the ESP-r integrated simulation package. Essentially, the equation-sets defining each domain are processed by customised solvers, while the domain interactions are handled by ensuring that the equation-sets for a given domain are established and solved as a function of information defining the evolution of any coupled domains. An earlier version of this paper appears in the proceedings of Building Simulation’99 [J.A. Clarke, Proc. Building Simulation’99, 1999] [1].     

The adaptive simulation of convective heat transfer at internal building surfaces

A flow responsive algorithm was devised and implemented within the ESP-r simulation program to advance the modelling of convective heat transfer at internal building surfaces. Empirical methods were extracted from the literature and a new method for characterizing mixed flow was created to provide the algorithm with a basis of 28 convection coefficient correlations. Collectively these methods can calculate convection coefficients for most flows of practical interest in building modelling. Working with this suite of correlations, the algorithm dynamically controls the modelling of convection by assigning appropriate equations to each internal surface each time-step of the simulation.     

Implementation and verification of the IDEAS building energy simulation library

Building and district energy systems become increasingly complex, requiring accurate simulation and optimization of systems that combine building envelope, heating ventilation and air conditioning, electrical distribution grids and advanced controllers. Hence, it becomes more challenging for existing simulation tools to provide integrated solutions for these multi-physics problems. Moreover, common building simulation frameworks tightly integrate model equations and their solvers in the program code, which affects model transparency and hampers tool extensions. This is contrasted by equation-based tools such as Modelica, for which different solvers can be used. In this context, the Integrated District Energy Assessment by Simulation (IDEAS) library is developed. After a recent development shift towards more detailed, multi-zone models, this paper presents a comprehensive, well-documented, overview of the buildings part of IDEAS. This includes new computational aspects of the library, improved usability aspects, an updated intercomparison with BESTEST and a verification based on IEA EBC Annex 58.     

Design of a distributed simulation environment for building control applications based on systems engineering methodology

The analysis of innovative designs that distributes control to buildings over a network is currently a challenging task as exciting building performance simulation tools do not offer sufficient capabilities and the flexibility to fully respond to the full complexity of Automated Buildings (ABs). For that reason, this paper deals with the design and development of a middleware for distributed control and building performance simulations that has been carried out to study and analyze the impact of control systems on building performance applications (i.e., building indoor environments) over a network, rather than costly and time-consuming experiments. The paper also presents a model-based Systems Engineering (SE) methodology for development and design of distributed control and building performance simulations involving two or more different software tools over a network. The main objective of this framework is to run-time couple one or multiple building performance simulation tool(s) with a control modelling environment over a network in order to similarly represent Building Automation and Control Systems (BACS) architecture in a simulation.     

Energy demand and indoor climate in a low energy building—changed control strategies and boundary conditions

Energy demand in the built environment is an important issue. In Sweden, 39% of energy use originates from the building sector, and this figure is increasing. Several attempts have been made to improve the energy use, for example low-energy houses, which are built with the aim of decreasing the use of energy, but still providing a good environment for the occupants. An energy simulation program, ESP-r, was used for simulation of the energy requirement and indoor climate in a well-insulated terraced house in Sweden. The building model was compared to measured values from the real object. A computational fluid dynamics (CFD)-model for one room was used to simulate and visualize the airflow and temperature pattern. Increased set-point temperature increases the power demand by about 200 kWh/°C. Thinner insulation increases the heat demand but decreases the demand for passive cooling by airing and deteriorates the indoor climate. Different types of windows affect both the energy demand and the indoor climate significantly. Load management was simulated by restriction on the heating possibilities and an economical comparison was made to investigate the advantage of such an operation. The extra insulation has a payoff time of about 38 years at common Swedish energy prices.     

Reduction of greenhouse gas emissions from UK hotels in 2030

The feasibility of halving greenhouse gas emissions from hotels by 2030 has been studied as part of the Carbon Vision Buildings Programme. The aim of that programme was to study ways of reducing emissions from the existing stock because it will be responsible for the majority of building emissions over the next few decades. The work was carried out using detailed computer simulation using the ESP-r tool. Two hotels were studied, one older and converted and the other newer and purpose-built, with the aim of representing the most common UK hotel types.     

DeST — An integrated building simulation toolkit Part I: Fundamentals

Many building simulation programs have been developed all over the world since the computer-aided simulation technology was first applied in the 1960s. In early 1980s, Tsinghua University has started to develop a new building simulation tool DeST with the aims to benefit for practical and research use of building simulation related applications in China. DeST can be used to simulate and analyze both building energy consumption and HVAC (heating, ventilation and air-conditioning) system. It has been designed to aim improving the reliability of system design, to ensure the quality of the system performance, and to reduce energy consumption of buildings. This paper reviews the development history, state-of-the-art on the development of building simulation technology and introduces the main objective, structure, and core programs of DeST. The analytical verifications, inter-program comparisons, and empirical validations of DeST are also presented in this paper. The application of DeST will be introduced in part II of the companion paper.